This invention relates to an improved mechanism for locking and releasing a telescoping member and more specifically relates to an improved trekking pole.
The general concept of extending a cylindrical rod by using a series of concentrically nested hollow members to provide a retracted position of a shortened length and an extended second length that is adjustable between the shortened length and a fully extended length is well studied in this art. However, in the art the locking mechanism to adjust one telescoping member relative to another has not satisfactorily provided a quick, lightweight, and secure means for such and, accordingly, improvement is needed.
As background, such attempts at providing locking mechanisms for telescoping members include a locking mechanism for telescoping tubing described by Pickles in U.S. Pat. No. 4,324,502 issued on 1982 Apr. 13. Therein Pickles teaches a concentric plug having a collar. The plug fits snugly in the end of the inside tube and is fixed against rotation by means of a transverse pin that extends through the inside tube, but is flush with its outside surface. The locking mechanism includes a short cylinder that has an outside diameter about the same as the outside diameter of the inside tube. This plug includes a peripheral groove that receives an o-ring that creates a friction fit between the plug and the inside wall of the larger diameter tube. Thus, at any given position where it is desired to lock the two tubes together in a fixed longitudinal position, the inner tube is rotated on its axis relative to the outer tube, which in turn causes a wedging action of the o-ring and plug relative the inside wall. This approach, however, has limitations in that the amount of frictional force of the o-ring and plug can easily be overcome under normal use both from degradation of the o-ring over time and because the surface area of the o-ring in contact with the inside wall is not sufficient to support the pressures exerted on the pole when used as a trekking pole.
Another type of telescoping concentric members includes a mast type device such as a telescoping mast with improved holddown-locking mechanism taught by Adams et al. in U.S. Pat. No. 5,163,650 issued on 1992 Nov. 17. Adams et al. teaches an improved locking system that includes a lock bar near the lower end of each lower section, a locking assembly on the upper end of each intermediate section, and a lock actuator stud on the upper ends of each of the intermediate and bottom sections. The lock assembly includes an inwardly projecting collar and a rotatable disk. The lock actuator stud and lock disk have mating engagable cam surfaces. Finally, a splined spring loaded nut carried by each mast sections engages a multiple lead axial screw to extend and retract the telescoping mast sections. One limitation of this device includes a reliance on rotating sections of mast and a screw drive for extending those sections: This adds complexity and in turn, makes such a device costly to build, maintain, and repair. Additionally, while the mechanism described by Adams et al. is suited for supporting adjacent telescoping sections from retracting unexpectedly, it is poorly suited for supporting additional weight that might be placed on the end of the upper most telescoping member, for example if the mast were used to support the weight of a person hiking, or supporting the weight of a light, a camera, microphone, and such.
Another adjustable length telescoping member is described by Liu in U.S. Pat. No. 5,651,565 issued on 1997 Jul. 29. Liu teaches an outer tube member and an inner tube member slidable inside the outer tube. An expansion member arranges within the outer tube member and consists of at least two tapered members each having innermost and outer most portions. The expansion member also carries an outer tube pressure member shaped to wedge between the expansion member an an inner surface of the outer tube. Liu teaches that pressure between (caused by friction) the inner surface of the outer tube and the expansion member is sufficient to hold the outer tube in relative position to the inner tube. However, as many experienced mountaineers, skiers, backpackers, and back-country explorers can attest, this friction hold device does not adequately hold the relative position of the inner and outer tubes when placed in use to support the weight of an uphill walker or climber, or a gear-laden user.
Yet another telescoping pole system is described by McMillan, III in U.S. Published Application No. 2010/0254751 published on 2010 Oct. 7. McMillan, III teaches a pole system having a first and second pole and a deforming member with a retaining element. The retaining element deforms when the user exerts pressure by means of a control button connected to a spring mechanism. The retaining element deforms, or flattens, thus dis-engaging the retaining element from a mating element in the pole piece. The McMillan, III system improves over the common friction fit adjusting mechanism common in the art by providing a rudimentary mechanical lock. Yet, improvements over McMillan are still needed to provide a more simple system, that is more robust and provides greater mechanical interlock than taught by McMillan, III.
Other known locking and adjusting mechanisms are known in the art, but bear little relevance to the current invention. Such teachings include an integrated handle for telescoping tubes as described by Hui in U.S. Pat. No. 5,669,102 issued on 1997 Jul. 23; a telescopic hand tool with locking mechanism described by Bart et al. in U.S. Pat. No. 5,363,727 issued on 1994 Nov. 15; and a telescoping rail with locking mechanism described by Wojcik in U.S. Pat. No. 5,181,782 issued on 1993 Jan. 26.